Indirect observations of electric fields at comet 67P

Moeslinger, AnjaUmeå universitet,Institutionen för fysik,Swedish Institute of Space Physics, Kiruna, Sweden (författare)

No spacecraft visiting a comet has been equipped with instruments to directly measure the static electric field. However, the electric field can occasionally be estimated indirectly by observing its effects on the ion velocity distribution. We present such observations made by the Rosetta spacecraft on 19 April 2016, 35 km from the nucleus. At this time comet 67P was at a low outgassing rate and the plasma environment was relatively stable. The ion velocity distributions show the cometary ions on the first half of their gyration. We estimate the bulk drift velocity and the gyration speed from the distributions. By using the local measured magnetic field and assuming an E × B drift of the gyrocentre, we get an estimate for the average electric field driving this ion motion. We analyze a period of 13 hr, during which the plasma environment does not change drastically. We find that the average strength of the perpendicular electric field component is 0.21 mV/m. The direction of the electric field is mostly anti-sunward. This is in agreement with previous results based on different methods.

Nilsson, HansUmeå universitet,Institutionen för fysik,Swedish Institute of Space Physics, Kiruna, Sweden(Swepub:umu)hani0062 (författare)
Stenberg Wieser, G.Swedish Institute of Space Physics, Kiruna, Sweden (författare)
Gunell, HerbertUmeå universitet,Institutionen för fysik(Swepub:umu)hegu0051 (författare)
Goetz, C.Department of Mathematics, Physics and Electrical Engineering, Northumbria University, Newcastle-upon-Tyne, United Kingdom (författare)
Umeå universitetInstitutionen för fysik (creator_code:org_t)

Ingår i:Journal of Geophysical Research - Space Physics: American Geophysical Union (AGU)128:92169-93802169-9402

Av författaren/redakt...: Moeslinger, Anja; Nilsson, Hans; Stenberg Wieser, ...; Gunell, Herbert; Goetz, C.

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